A related art headlamp system is configured to automatically control a light irradiation direction of a headlamp to enhance traveling safety of a vehicle. For example, the system includes a leveling device configured to control and change the light irradiation direction of the headlamp in a vertical direction in accordance with variations in a pitch angle of the vehicle (i.e., an inclination angle of the vehicle along a front-rear direction of the vehicle) which may be caused by a change of occupants or a change of a load carried on the vehicle. The system also may be include a swiveling device configured to control and change the light irradiation direction of the headlamp in a horizontal direction so as to follow variations in a steering angle. The swiveling device includes a cornering lamp device having multiple lamp units in the headlamp and configured to automatically turn on or off of the lamp units to control and substantially change the light irradiation direction of the headlamp in the horizontal direction. The system may also include a lamp headlamp cleaner configured to automatically clean a front cover of the headlamp.
The headlamp system having such multiple of functions includes an electronic control unit (ECU) for centralized control of the respective functions. The ECU is programmed to carry out the respective functions. More specifically, the ECU is configured to detect variations in the pitch angle, the steering angle, and/or dirt on the headlamp and to automatically control, based on the detected data, the leveling device, the swiveling device and/or the lamp headlamp cleaner. However, the vehicle type differs depending on grade and specifications of the vehicle and, if the ECU is prepared for each type of vehicle, manufacture and management of the ECUs become onerous. In view of this, there is proposed an ECU of a generalized type. This type of ECU is installed with a program that can be commonly used for different types of vehicle. Vehicle constants, which differ for each type of vehicle, are stored in a memory of the ECU in advance, so that a vehicle constant that corresponds to the type of vehicle to be controlled can be selected to carry out a normal control corresponding to the vehicle type.
For example, a related art auto-leveling system for a vehicle headlamp uses such an ECU. According to this related art system, when a specification signal for selecting a vehicle constant that corresponds to a vehicle type is entered into the ECU, a specification signal recognition section of the ECU recognizes the vehicle type, and the ECU transmits a specification signal that corresponds to the recognized vehicle type to the outside for verification (see, e.g., JP 2006-160036 A).
Some ECUs of this type have a diagnosis communication function. By using the diagnosis communication function, reception and transmission of the specification signals are carried out. The ECU having the diagnosis communication function obtains error codes (i.e., diagnostic trouble codes (DTCs) during a self-diagnostic operation), and stores the DTCs in a memory, and reads the DTCs when needed. These codes are specific to different types of vehicle. Therefore, when specifications of a vehicle are changed as the result of an addition or replacement of options to the vehicle and thus the vehicle is treated as a different type, the DTCs stored before the change of specification become inconsistent, which may cripple the system. This is not limited to the error codes. For example, when an ECU stores initial setting values serving as reference values for control, such as a reference vehicle height for initializing a leveling device, a reference steering angle for initializing a swiveling device, and a dirt reference value for initializing a headlamp cleaner, and specifications of the vehicle are changed (e.g., added, deleted or replaced). The initial setting values previously stored in the memory of the ECU and new initial setting values to be newly set for the changed specifications may interfere with each other, which may cause a problem in the system.
In order to address these issues, the ECU may be reset when the vehicle type is changed so as to clear the error codes and initial setting values stored in the memory, and store new error codes and initial setting values that correspond to the current vehicle type. However, in this case, the system cannot be operated until storage of all initial setting values necessary for the system is completed. Thus, during storage of the initial setting values, normal control operations of the system are stopped. For example, the normal control operation by the leveling device is stopped until a reference vehicle height is initialized, the normal control operation by the swiveling device is stopped until a reference steering angle is initialized, and the normal control operation by the headlamp cleaner is stopped until a dirt reference value is initialized. Therefore, the normal control operations by the leveling device and swiveling device are stopped until the initializations of the reference vehicle height and the reference steering angle are completed and thus, during such time, the operations of the entire system is stopped. Accordingly, recovery of the system takes time.
Sensors such as a vehicle height sensor and a steering angle sensor are coupled to the ECU to detect the pitch angle and the steering angle. Based on detection outputs from the sensors, the ECU controls, for example, the leveling device and the swiveling device. The system may be configured to carry out a failsafe operation such that the ECU monitors the outputs from the respective sensors and, when the ECU determines that sensor outputs are abnormal, control operations of the leveling device and the swiveling device are stopped. However, when it is determined for example that the steering angle sensor is abnormal, control operation of the swiveling device and also control operation of the leveling device, which may not be associated with the steering operation, are stopped. In other words the entire system is stopped, until the steering angle sensor is recovered.